John Gagnon calls himself the Appliance Doctor, working out of Oshawa, Ontario. He picked up an old dryer off of the street and brought it into studio to show that it should never have been thrown away.
In less than a minute he had opened up the front (wedge a screwdriver into the slot between the face and the top in the front and pop the top open -- then take out two screws and the front panel lifts off), removed the drum (release the belt from the motor and the drum just lifts forward), replaced the two balancing wheels (pull the retaining pins with a screwdriver, slide the old wheels off and the new ones on), and put on a new drive belt. The Tune-Up kit sells for around $35 and stops all that vibration that you hear from your old machine. They are available in any appliance repair store.
The one he brought in was probably thrown out because no one ever cleaned the filter, which then burned. What a waste.
He also recommends replacing all rubber hoses with rubber/metal jacket hoses. The rubber ones will eventually burst under the constant pressure and cause a flood.